U.S. Pat. No. 4,774,977 for FULL FLOW MULTIPORT BUTTERFLY VALVE (incorporated herein by reference) discloses a multiport valve with union plumbing connections utilizing a disc diverter permanently housed in a spherical two piece welded housing. The multiport disclosed in the '977 patent is described as a nonserviceable but easily replaced multiport valve with low resistance.
A process for manufacturing the multiport valve disclosed in the '977 patent is described therein as starting with the separate molding of top and bottom valve body halves. After molding is complete, the valve body halves are deflashed. The bottom valve body half is then positioned in a vibration welding fixture, the diverter is positioned on the splined shaft located in the bottom fixture, the top body half is positioned thereover and the two valve body halves are welded by vibration welding. The four union port flange faces are then machined to remove welding fixture flanges. O-ring glands are then machined into the faces of the union pipe parts. The inside of the valve is then deflashed at the weld area using an ultrasonic scalpel. Although the scalpel may be automatically indexed to accurately follow the port, ramp and seal areas, removal of the weld flash is necessarily an individually monitored process.
While the manufacturing steps outlined above are relatively straightforward, it is now believed that the tooling required to set up machinery to manufacture individual multiport valves like those described in the '977 patent is relatively expensive. The expense is heightened, in part, by the close tolerances required to manufacture the valve body components and the disc diverter components, which sealingly engage the valve body components.
In any case, the multiport valve described in U.S. Pat. No. 4,774,977 was primarily intended to satisfy a perceived process flow design need for a disposable multiport valve. There remains a need, however, for a serviceable multiport valve. For example, operational requirements may include the ability to disassemble and visually inspect a multiport valve if flow blockage has occurred. Disassembly of a welded multiport valve is typically impractical. Other fluid processing operations may require replacement of disposable valve elements such as O-rings, disc diverters, and elastomeric dynamic seals, rather than allowing for discard and replacement of an entire multiport valve. Unserviceable, disposable, welded multiport valves would not be expected to satisfy the operating requirements of such a plant.
It is therefore an object of the present invention to provide a multiport valve which is economical to manufacture and does not require component welding or deflashing.
It is also an object of the present invention to provide a multiport valve which is serviceable.
It is a further object of the present invention to provide a multiport valve having the aforementioned characteristics, in which fluid leaks through internal leak paths is prevented.
It is against this background that the significant improvements and advancements of the present invention have taken place in the field of butterfly valves.